This invention relates generally to battery packs and, more particularly, to battery packs for cordless power tools.
Cordless products which use rechargeable batteries are prevalent throughout the workplace as well as in the home. From housewares to power tools, rechargeable batteries are used in numerous devices. Ordinarily, nickel-cadmium or nickel-metal hydride battery cells are used in these devices. Since the devices use a plurality of battery cells, the battery cells are ordinarily packaged as battery packs. These battery packs couple with the cordless devices and secure to the device. The battery pack may be removed from the cordless device and charged in a battery charger or charged in the cordless device itself.
FIGS. 1-3 illustrate a typical battery pack 10, which includes a bottom housing 11, a plurality of cells 12 disposed within the housing, a cell 13 disposed on the plurality of cells 12, and a terminal block 14 disposed on cell 13. Persons skilled in the art will recognize that the terminal block 14 and cells 12, 13 are electrically connected in a manner well known in the art, and that such electrical connections are not shown for the sake of clarity. Also, persons skilled in the art are referred to U.S. Pat. No. 5,144,217 for further information on a typical prior art terminal block 14.
A pack cover 15 carrying a tower 16 is disposed on housing 11 so as to contain cells 12, 13 therein. Tower 16 has an aperture 17 exposing terminal block 14 for electrical connection to the power tool (not shown). The pack cover 15 may be held in place via screws 19, or other means, so as adhesives, molten plastic, etc.
Typical battery packs include at least one latch mechanism 18 for latching the battery pack 10 to the power tool, or cordless device. Latch mechanism 18 typically includes a button 18B disposed on housing 11, a latch hook 18L movably connected to button 18B and movable between a latching position and an unlatched position, and a spring 18S for biasing latch hook 18L towards the latching position. Accordingly, in order to unlatch a battery pack from the power tool, the user needs to press button(s) 18B with one hand, moving latch hook 18L towards the unlatched position, and pull out the battery pack 10, while holding the power tool with the other hand.
Typically battery packs 10 have two buttons 18B on opposing walls of housing 11. Accordingly, the operator needs to bridge the composite distance of A, B and C, i.e., the lengths along the housing 11, in order to press both buttons 18B and unlatch battery pack 10. However, as the number of cells 12 is increased to obtain higher voltages, the composite distance (A+B+C) is also increased, until the operator cannot easily reach both buttons 18B.
In accordance with the present invention, an improved battery pack is employed. The battery pack includes a housing with opposing walls, a plurality of cells disposed within the housing, at least two terminals electrically connected to the cells, a latching mechanism disposed on each opposing wall for latching the battery pack to a cordless device, each latching mechanism including a latch and a button disposed on the wall for moving the latch between unlatching and latching positions, the latching buttons being disposed along a first plane, the first plane being substantially vertical, wherein the number of cells disposed along the first plane is smaller than the number of cells disposed along a second plane substantially parallel to the first plane. The battery pack may also include a stacked cell disposed on the plurality of cells. The stacked cell may be disposed along the first plane. However, the stacked cell is not included in the number of cells disposed along the first plane.
Additional features and benefits of the present invention are described, and will be apparent from, the accompanying drawings and the detailed description below.